1. Field of the Invention
This invention relates in general to oil and gas well drilling equipment, and in particular to a coupling device that connects into the upper end of the drill string to enable it to be broken out and made up with less torque than normally required.
2. Description of the Prior Art
In recent years, top and side drive oil and gas well drilling rigs have been commercially available. In these types of drilling rigs, drive equipment for rotating the drill pipe will be supported by the derrick. The drive assembly may be a top drive type as shown in U.S. Pat. No. 4,421,179. Or the drive assembly may be of a side drive type such as shown in U.S. Pat. No. 4,875,529. In both cases, a drive mechanism in the derrick will impart torque to the drill string.
Top and side drive drilling systems enable an operator to drill with a triple stand of pipe, rather than a single stand as with a kelly bushing type of drill rig. Particularly in the case of highly deviated wells, it enables a driller to ream as he is pulling out of and running into the hole. During reaming, the driller will rotate the pipe.
While reaming out of the hole, the top connection of each triple stand will be broken out high in the derrick. Also, if reaming while, going into the well, the top connection with the rotary drive spindle must be made up while high in the derrick. These operations require power make up and break out equipment in the derrick. If the make up and break out equipment does not have a back up, tongs must be employed on the rig floor for back up.
In U.S. Pat. No. 4,658,915, a coupling is shown for connection between the drive spindle and the top of a triple stand. This coupling will break out at a lower torque than making up. This avoids a need for a back up tong high in the derrick. Rather, the back up tong will be located at the rig floor, and the drive spindle will be rotated in reverse to break out the top connection. The break out torque, while lower, is still substantial.